Radiation Reliability of BEOL Compatible Ga-Doped Indium Oxide MOSFETs for eDRAM Applications

This work addresses a key bottleneck in radiationhardened computing: achieving high-density embedded memory in monolithically stacked (M3D) systems without relying on areainefficient SRAM or radiation-sensitive scaled Si access devices. We evaluate back-end-of-the-line (BEOL) compatible Ga-doped indium oxide (IGO) MOSFETs as access transistors for vertically integrated 1T-1C embedded DRAM (eDRAM) under both ionizing and displacement-damage radiation. Devices are subjected to60Co gamma total-ionizing-dose ($\gamma$-TID) up to 10 MRad(air) and neutron fluence up to$\mathbf{1 0}^{\mathbf{1 5}} \mathbf{n} / \mathbf{c m}^{\mathbf{2}}$. IGO MOSFETs exhibit exceptional$\gamma$-TID tolerance: transfer characteristics, threshold voltage ($\mathbf{V}_{\mathbf{T h}}$), and effective mobility remain statistically invariant up to 10 MRad, and sub-gap density-of-states (DOS) extraction from multi-frequency CV confirms negligible ionization-induced defect generation. In contrast, neutron irradiation produces pronounced displacement damage, manifested as positive$\mathrm{V}_{\text{th}}$shifts, mobility degradation, and increased mid-gap and band-tail defect densities. Bias-temperature-instability (BTI) measurements show radiationaccelerated parameter drift; enhanced PBTI is consistent with activation of deep traps in the$\text{HfO}_{2}$gate dielectric, while increased NBTI is consistent with radiation-assisted hydrogen diffusion. Calibrated TCAD reproduces these trends, linking$\boldsymbol{\gamma}$TID primarily to modest interface-state increases and neutrons to broader/deeper defect spectra. System-level analysis indicates IGO-based 1T-1C eDRAM achieves$\boldsymbol{\sim} \mathbf{5 0 0} \boldsymbol{\times}$higher retention than silicon baselines and only a 2% retention penalty at 10 MRad (vs$\boldsymbol{\sim} \mathbf{4 2 \%}$for Si FinFETs), positioning BEOL IGO as a scalable access-device platform for dense, radiation-hardened monolithic eDRAM.